High frequency circuit



Feb. 18, 1936. F; A. KOLSTER ,499

HIGH FREQUENCY CIRCUIT Fild Oct. 51, 1954 Siam 2.9

frezZerz'aZA.fioZaier INVENTOR ATTR Y Patented Feb. 18, 1936 UNITEDSTATES PATENT OFFICE HIGH FREQUENCY CIRCUIT Application October 31,1934, Serial No. 750,819

6 Claims.

This invention relates to high frequency circuits, and particularly totank flywheel frequency determining circuits especially useful inconnection with vacuum tubes employed as oscillation generators.

An object of the invention is the production of such a tank circuit, thefrequency characteristic of which is substantially constant for widevariations in temperature of the elements 10 thereof.

Another object of the invention is the provision of such a tank circuitformed as a, simple, compact unit, easily mounted and adjustable over afairly wide range of operating frequencies.

In one of its aspects the invention is an improvement over my co-pendingapplication Ser. No. 637,564, filed October 12, 1932, and particularlyas disclosed in Figures 1 to 3 thereof.

A tank circuit embodying the invention is particularly useful in highfrequency radio systems employing frequencies of 60,000 kilocycles, thatis, for wavelengths of five meters and below.

Other objects of the invention will appear from the description andclaims.

An embodiment of the invention is illustrated in the accompanyingdrawing, wherein:

Figure 1 is a front elevation, partly in section, of the unitary tankcircuit;

Figure 2 is a broken right end elevation of the device of Figure 1; and

Figure 3 is a top plan of the mechanism for adjusting the tank circuit.

The tank circuit according to the invention comprises a closedoscillatory circuit containing inductance and capacity elements. Theprincipal inductance element is formed as a tube of high conductivitycopper. This tube I is connected at each end by coupling rings 2 toextension tubular members or end tubes 3 and 3a, which are also of highconductivity copper. The

tubular member I with the end tubes and coupling rings are held togetheras a unit by means of supporting metallic blocks 9 and co-operating tierod III which extends through said members '45 and is provided with nuts29 which hold the assembly firmly together. The supporting blocks 9 areeach provided with two openings So for the passage of bolts employed tofasten the structure to supporting insulator pillars 30.

Supported upon the left end tube 3a is a cupshaped member 3| havingradially projecting flanges l3 which serve as condenser plates. Thecup-shaped member 3| has a split tubular extension 32 surrounding theend tube 3a and provided with a pair of flanges 33 on opposite sidesthereof, through which bolts extend for clamping the cup-shaped member3| in proper position on theend tube 3.

A second cup-shaped member 35 is rotatably supported on the right endtube 3 by a tubular 5 extension 36 fitting over tube 3. This cup-shapedmember 35 has radially extending flanges [4 similar to flanges l3 on theother cup-shaped member. These flanges I I are the same in number as theflanges i3 and serve as condenser plates. 10 Flanges l3 form condenserplates of the stator of the condenser, while flanges [4 form thecondenser plates of the rotor of the condenser.

As shown, the rotor and stator condenser plates are staggered and thereare eight of each. This 15 number may be increased or decreased, butwith eight, the tuning angle of the condenser is about 15 degrees.

The rotor 35 of the tank circuit condenser may be rotated to vary thedistance between the rotor 20 and stator plates by means of a wormdrive. This worm drive comprises a worm gear 8 carried by a worm shaftI2 rotatably supported in a drive bracket l I, the worm 8 being fixed toshaft l2 and spaced from the arms of the bracket by means of spacingsleeves 8a. The bracket II is formed at its lower end so as to surroundend tube 3 and is split so as to be held firmly in clamped adjustedposition thereon. The worm 8 engages a worm gear segment 1 formed on an'30 annular plate 31 which surrounds the end tube 3 and is held inspaced relation thereto by being bolted or otherwise fastened to lugs 38provided on the rotor 35.

For operating the worm 8 a hand-wheel 39 is 5 connected to the shaft [2,an elongated insulator 40 being interposed between the hand-wheel 39,which may be of metal, and the worm shaft l2. The tank circuitordinarily will be mounted back of a panel, with the operatinghand-wheel in 40 front thereof.

The condenser rotor 35 is held yieldingly in its extreme left positionby means of a coil spring 4| surrounding end tube 3. This spring isinterposed between the annular member 31 carried by the 45 rotor and athrust ring 42 also surrounding the end tube 3 and positioned adjacentthe bracket ll. One end of this spring is fixed to the rotor by beingfastened under the head of the screw 22, while the other end is fastenedto an extending lug 43 on the bracket II by being fastened under thehead of the screw 23.

The spring also assists in holding the rotor in adjusted position, andprevents any backlash in 55 the operating mechanism from afiecting theadjusted position of the rotor.

The cup-shaped stator 3| and rotor 35 with the condenser plates may becast of bronze, and then copper-plated. To prevent corrosion the statorand rotor may be lacquered.

It will be noted that the coupling rings 2 are formed at one end asplugs 45 inserted in the ends of the central tubular inductance :member'.I. The oppositeside of each of the rings 2is formed to receive endtubes 3 and 3a. Each coupling ring 2 is also formed with a conicalsurface "46 against which a like conical surface on the stator and therotor is held in firm electrical contacting engagement. This electricalengagement between the mating conical surfaces on the stator 3| and thecoupling ring 2 is maintained by the stator being held inclampedpositiomwhile such contact between the mating conical surfaces ofthe rotor and the other coupling ringmaintained due to the action .ofthe coil spring 4]., so that as .the rotor is adjusted the said contactis maintained.

The particular construction of employing a central tubular inductancelandend tub,es 3 with coupling rings 2 permits the use of inductancetubes 1 of differentrdiameter,.southatthe operating frequency range ofthe circuit may .be altered. To make suchalteration it is merelynecessary to provide central .tubes of other diameters and othercoupling rings with the plug .ends thereof or" appropriate diameters. Atubular inductance element of .sufiicient length may be employed therebyeliminating the coupling rings and end tubes.

The stator and rotor are, of course, maintained with their open ,facesin spaced relation. For

making electrical connection to the electrical midpoint of theinductance element of the tank laircuit, the tubular inductance element.1 .is provided with a clamp 18 surrounding the .tube. This clamp 18 maybe .heldin adjusted position by means of a set screw 4.1.

The length of the rotor and-stator condenser plates I3 and M is suchthat as the structure expands and contracts slightly under varyingtemperature conditions the area of Opposed plate surfaces will remainconstant. Thus, the varying conditions of expansion and contraction willhave no effect upon the capacity of .the tank circuit insofar as theplates of .the condenser element are concerned because the spacing andopposed area thereof remain constant. The expansion and contraction,under varying heat conditions, will, however, cause .some slight changesin capacity due .to the varying of the distance .between the oppositeopen ends of the stator and rotor. The capacity between the oppositeedges of these cup-shaped members is very small and forms only a verysmall part of the capacity in the tank circuit. The variations in suchcapacity between the opposing edges of these cup-shaped members may bereduced still further-by reducing the thickness of the wall ofthecup-shapedmembers at the 'opposing'edges, and/or by increasing thedistance between them.

The inductance of a tank circuit is formed by the central tube ltogether with the cup-shaped members 3| and .35. The inductancepathofthe tank circuit is, therefore, toroidal.

The resistance of the tank circuit is extremely .low, being of theorder-.of less ithanone-hundredth of an ohm.

Tank circuits embodying invention :have been constructed in which :forwavelengths of three meters, the capacity micro-micro-farads, theinductance approximately .05 micro-henries, and the resistanceapproximately .009 ohms, which gives a Q of upwards of 3000, the valueof Q being determined from the formula Q x/i- -v where L'istheinductance, R the ohmic resistance, and C the capacity of the tankcircuit. Such a tank circuit has been found to be very useful inconnection with vacuum tubes for the production of high frequencyoscillations.

In another practical embodiment of the invenit'iomt'he -tank circuitconstructed was capable of use in oscillation generator systems in theproduc- 31210151 :of wavelengths varying between three and five meters.By increasing the diameters of the central inductance tube I, theoscillations of shorter wavelengths are produced.

In tank circuitsembodying the invention, which have been constructed,the frequency stability has-been remarkably good. Thus, for temperaturechanges of 30 centigrade, there has been a change in frequency of :lessthan 2,000 cycles in 60,000,000.

Although the tank :cicrcuit has beenillustrated as being mounted withthe inductan'cetube l in horizontal position, the mounting may be suchas .to have the tube I extend vertically. When so mounted, insulatingpillars 30 will not be required forthe cup-shaped stator 3|willrest-uponandbe fixed directly to supporting insulators.

What is claimed is:

1. An electrical circuit comprising a metallic tube 'forming aninductance element of said circuit, a pair of dome-shaped metallicdevices mounted in spaced relation at opposite ends of said tube inelectrical contact therewith, one device being fixed and the otherrotatable relative .to said tube, flanges on both devices positioned to.form a variable capacity element of the said circuit and so that theseparation there-- is approximately 60 \of is variable by rotation, andmeans for rotating said rotatable device to vary the distance betweenthe flanges of said devices.

2. An electrical circuit comprising a metallic tube .iorming aninductance element of said circuit, a pair of dome-shaped metallicdevices mounted in spaced relation at opposite ends of said tube inelectrical contact therewith, one of said devices :being rotatablerelative to the other, and radially extending flanges on both devicespositioned to form a variable capacity element .of the said circuit andso that separation thereof is variable by rotation.

.3. .An electrical circuit comprising a metallic tube .-forming aninductance element of said circuit, a pair of dome-shaped metallicdevices mounted in spaced relation on said tube in electrical contacttherewith, one .of said devices being rotatable relative to the other,radially extending flanges on said devices positioned to .form avariable capacity element of said circuit and so that the separationthereof is variable by rotation, and means for rotating said rotatabledevice to vary the capacity between the said flanges.

4. An electrical device comprising, as a com- :posite' unit, a.conducting rod constituting an inductance element of an electricalcircuit, a pair of spaced conducting members electrically connected tosaid rod, one :being rotatable relative to the other, said membersforming a variable capacity element co-operating with said inductanceelement to provide a closed oscillatory circuit and being so positionedthat the distance therebetween is variable by rotation, and means forrotating said rotatable member to vary the distance between saidmembers.

5. An electrical circuit comprising, as a composite unit, a metallictube forming an inductance element of said circuit, a pair of domeshapedmetallic members mounted in spaced relation along said tube inelectrical contact therewith and co-operating with said element toprovide a toroidal inductance path, and a plurality of equally spacedradially extending flanges on each member, the flanges of one memberbeing staggered with respect to the flanges of the other and positionedto present opposing faces thereby to form multiply connected capacityelements of said circuit.

6. An electrical circuit comprising, as a composite unit, a metallictube forming an inductance element of said circuit, a pair ofdome-shaped metallic members mounted in spaced relation along said tubeand in electrical contact therewith whereby under varying operatingtemperatures said spacing varies due to expansion and contraction ofsaid tube, and radially extending flanges on said members positioned inopposing relation to form a capacity element of said circuit thecapacity of which is unaffected by variation in said spacing.

FREDERICK A. KOLSTER.

